1. Field of the Invention
The invention relates to a method for evaluating oscillation signals on rotor blades of wind power installations.
2. Description of Related Art
U.S. Pat. No. 7,883,319 describes a method in which the loading of rotor blades is determined and spectrally evaluated using accelerometers. The acceleration sensors generate an electrical signal which reproduces the oscillation state of a rotor blade. This electrical signal is further processed electronically by spectra being computed. A Fourier transform is named as the sole example for computing the spectra. The oscillations are excited by the operation of the wind power installation or by the wind which is incident on the blade.
German Patent Application DE 10 2009 029 280 describes an unbalance measurement in which the spectral power density is evaluated for evaluation of the oscillation signal. The unbalance is measured in a balancing machine, therefore not during operation of the article which is to be tested for its unbalance. The oscillation sensors are located on the balance machine on the bearings for the rotating body which is to be balanced.
In the automotive supply industry, components are subjected to a loading test on test benches by their being excited on a vibration table with specific signal shapes. Excitations with a shaker are also common. In the evaluations carried out there, the spectral power density is recorded. Attempts to transfer this type of evaluation to rotor blades of wind power installations dictate generally large and heavy devices for excitation of oscillations in the rotor blades or for application of loads to the rotor blades. Smaller devices as proposed in German Patent Application DE 20 2011 001 901 always necessitate shutdown of the wind power installation. Thus, these methods cannot be carried out during operation of a wind power installation.